This invention relates to camera systems, such as video camera systems with a lens coupling member, and more particularly to a lens coupling member which allows various photographic lenses to be interchangeably attached to a camera body.
In the past, camera bodies have operated with interchangeable fixed focal length lenses and zoom lenses to accomplish various photographic ends. To allow this, a mechanism on the camera body secures the lenses to the body.
Recently available photographic cameras may be classified as 35 mm cameras using photographic film, video cameras, 8 mm cameras, and others. These categories have respective individual photographic lenses designed and constructed in accordance with the image format of the camera.
However, it is possible to use photographic lenses of one camera category with cameras of another, for example, 35 mm cameras with video cameras. In other words, it is possible to utilize the photographic lens constructed for one image format with a camera body of a different image format.
However, to do this one need take into account the image circle of the lens. For example, in a video camera using a 2/3 inch image pickup tube, the diameter of the image circle is at least 11 mm, while in the 35 mm camera, it is at least 43.3 mm. Therefore, using photographic lenses for video camera on 35 mm cameras will very likely eclipse or shade the corners of the picture frame. Hence, satisfactory imaging performance cannot be insured over the entire area of the picture frame.
Conversely, when the photographic lenses for the 35 mm camera are mounted on video cameras, there is no possibility of eclipse, and no problem in respect to the image quality over the entire area of the frame.
In fact, generally speaking, photographic lenses primarily adapted for a large format, (i.e., large format lenses), for example for silver halide film cameras (i.e., large format cameras) can be used in place of lenses primarily adapted to a smaller format (i.e., small format lenses), for example, for video cameras (i.e., small format cameras).
However, with a large format photographic lens on a small format camera body, pencils of light rays enter the camera body and strike areas outside of the image frame. This introduces flare and ghost and lowers the image quality at the margin of the image frame because more than the necessary pencils of light rays arrive at the margin, and the light distribution becomes nonuniform over the entire area of the frame.
An object of the invention is to improve camera systems.
Another object of the invention is to avoid the aforementioned disadvantages.
Yet another object of the present invention is to provide a lens coupling member for use in attaching a large format photographic lens to a small format camera body which prevents unnecessary pencils of light rays from entering the camera body, and thereby to eliminate the aforementioned drawbacks.